Facing assembly for lens grinding tools and the like



June 13, 1967 D. J. HOENIG 3,324,6U3

FACING ASSEMBLY FOR LENS GRINDING TOOLS AND THE LIKE Filed Jan. 27, 1965 /4- FIG.

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I N VEN'IOR. DONALD J. HOE NIG ATTORNEYS 3,324,608 FACIN G ASSEMBLY FOR LENS GRINDING TOOLS AND THE LIKE Donald J. Hoenig, Thompson, Conm, assignor to Thompson Processing Co., Inc, Thompson, Conn., a corporation of t'lonnecticut Filed Jan. 27, 1965, Ser. No. 428,473 Claims. (Cl. 51-395) The present invention relates to an improvement in grinding and .abrading elements and more particularly to an improved facing or cover assembly for lens grinding tools and the like.

In the process of providing prescriptively accurate surfaces on limpid or transparent bodies such as ophthalmic lenses, it has been the practice to employ at least three basic lens producing operations. First is the rough grinding or curved generating operation which imparts an initial or basic curvature to the surface of a transparent body such as a lens blank. Today this operation is commonly accomplished by employing a curved diamond containing tool. Next, the limpid body containing the arcuate, rough ground surface is subjected to fine grinding or fining in an extremely precise and accurate manner to provide the desired optical correction and to produce a lens having a fairly smooth finish. The step of fining is commonly el'fectuated by the action of an abrasive slurry against the generated surface under the compressive motive force of an appropriate surfacing tool. Subsequent to the fining operation the lens is polished using a soft pad which may be attached to the same curved tool used in the fining operation.

Since it is required that exactitude and precision be obtained it has been the practice to utilize in the fining operation a highly precise, curved surfacing tool generally made from cast iron and having on the working face thereof the desired curvature to be reproduced. Because the abrassive wear resulting from continuous use causes some inaccuracy in the surfacing tool, it has become the practice to employ a facing or cover on the tool which may be readily replaced after each fining operation, thus prolonging the life of the tool while obtaining the desired optical perfection.

Recently, there has been employed in the fining operation a facing or covering made of formainous material such as wire mesh or screening which may be attached to the lens grinding tool. However, due to the thickness of the Wire which necessarily must be employed, it has been found necessary to alter the surfacing tool so as to compensate for the thickness of the Wire mesh, Additionally, it has been found that uncoated wire has a tendency to loose small slivers of the wire during the fining operation. These small pieces of wire tend to clog the abrasive slurry pumping apparatus and in many instances have been found to scratch the lenses, particularly when plastic lens blanks are being finished. More importantly, it has been found that the wet slurry of the abrasive which is used in combination with the vibrating action of the abrasive fining operation causes rupture or failure in the adhesive securing the screen to the tool, resulting in slippage from the surfacing tool and ruining of the lens.

Accordingly, it is an object of the present invention to provide a facing or cover assembly for a lens grinding tool which is free from the above limitations and difficulties while at the same time providing both a mechanical improvement and an economic advantage over facings employed heretofore.

An additional object of the invention is to provide a facing or cover assembly which is dimensioned so as to obviate the necessity of providing compensation on the surfacing tool yet is strong and rigid enough to provide 3 ,324,608 Patented June 13, 1967 dimensional stability during the fining operation without sacrificing the precision and accuracy required for such operations.

Another object of the present invention is to provide a facing assembly which eifectuates closer tolerances of operation and more accurate and precise fining of the lens blank while preventing substantial leakage of the abrasive slurry to the adhesive and preventing failure thereof resulting from slippage.

A further object of the present invention is to provide a facing or cover assembly for a lens grinding tool which can be quickly and easily attached to the tool yet is made in such a facile and economical manner as to permit disposal thereof after a single grinding operation thereby assuring retention of accuracy while substantially lowering the number of lenses which must be rejected during production.

Other objects will be in part obvious and in part pointed out more in detail hereinafter.

The invention accordingly consists in the features of construction, combination of elements and arrangement of parts which will be exemplified in the construction hereafter set forth and the scope of the application which will be indicated in the appended claims.

In the drawing:

FIG. 1 is a top plan view of the facing or cover assembly of the present invention; and

FIG. 2 is an enlarged sectional view taken along the line 2-2 of FIG. 1.

Referring now to the drawing in detail, the facing or cover assembly of the present invention, generally designated 10, is adapted primarily for covering the working surface of a lens grinding tool. Although the assembly may possess a variety of specific configurations or shapes, in the embodiment chosen for illustrative purposes the cover assembly 10 is continuously arcuate in outline, being provided with a generally circular outer edge 12 and a plurality of radial slots 14 inwardly extending from edge 12 andterminating in the curved areas 16 located inwardly slightly greater than two-thirds the length of the radii. The slots 14 are arrangedso as to permit the facing to assume the arcuate contour of the working face of the particular tool utilized. As best shown in FIG. 2, the facing assembly 10 prior to .its attachment to the surfacing tool comprises a three layer structure. The top or outermost layer 18 is a continuous, imperforate sheetlike structure made from generally tough, flexible materials of foil thickness. Although any material of similar thickness which will withstand the abrasive forces employed in the fining operation may be employed, it has been found that best results are obtained when, layer 18. is made of metal, such as tin,.copper, aluminum or steel foil. Theactual size or thickness of the material may vary depending upon its toughness and durability, as well as on the hardness of the lens blank-material and abrasive employed. Foils as thick as 0.010" have been advantageously utilized, although preferably the material should exhibit a thickness of between 0.001" and 0.005.

The bottom or. inner surface 20 of the layer 18 is in intimate physical contact with an imperforate adhesive layer 22 which is of substantially uniform thickness and completely conforms with the lower surface 20. The adhesive layer 22, as shown, is of substantially lesser thickness than layer 18 and covers the entire surface 20 throughout its full extent. Among the adhesives which may be generally clear in color, highly tacky, and is substantially resistant to water, heat, and the tendency to creep, possesses a natural rubber base dispersed or dissolved in a rather volatile organic solvent and may be applied by conventional coating methods such as with a brush, roller, or doctor knife. After application the film may be readily dried until it becomes tacky to the touch and does not transfer.

The final layer 24 abuts adhesive layer 22 and acts to protect the adhesive from dirt or other materials detrimental to its bonding capacity. Although the pressure sensitive adhesive readily disengages from most materials it contacts, it is generally preferred to employ release paper or the like, for example, silicone treated fabric or plastic for the layer 24. When the facing is to be applied to the surface fining tool, the protective layer 24 can then be easily removed without the possibility of damaging the adhesive. The outermost or top surface 26 of the layer 18 is modified so as to facilitate the continuous and uniform distribution of the abrasive slurry during the fining operation. This modification is accomplished in such a manner as to maintain the imperforate nature of the facing while improving the strength thereof. As shown in FIG. 1, surface 26 contains a plurality of indentations or depressions 28 which impart a knurled or wafiled configuration to the facing. Such indentations may, of course, be randomly oriented and need not take any definite configuration. It is sufficient only that the undulations be of sufiicient number and proper arrangement so as to facilitate the uniform movement of the abrasive slurry during the fining operation.

As best shown in FIG. 2, the undulations in the facing assembly preferably extend through both the outer foil layer 18 and the adhesive layer 22. Thus there is provided between the flat release layer 24 and the indentations 28 a plurality of resilient air pockets 30 which act as a very slight cushion or buffer. Accordingly, the undulatory facing provides the plural advantage of facilitating uniform distribution of the abrasive slurry and compensating for slight variations therein while ensuring against slippage between the facing and the tool. The latter effect is achieved by the use of the air pockets 30 which upon compression provide increased contact between the pres sure-sensitive adhesive and the tool and upon expansion tend to behave .in a manner similar to hundreds of small suction cupsQThus, the slippage experienced .by screen or wire facings is substantially eliminated.

The facing assembly of the present invention can be readily manufactured by coating one side of a sheet of flat metal foil, such as aluminum foil, with a pressureresponsive adhesive and subsequently drying the adhesive to a tacky state by removing the solvent therefrom. After the adhesive has .been properly applied and dried the dual layer structure is then subjected to suitable means, not shown, which impart thereto the knurled or undulated appearance, after which theadhesive layer is covered with a protective release paper or the like which, as best seen in FIG. 2, only contacts the depressed areas of the dual layer structure. It will, of course, be appreciated that the paper 24 may be placed in contact with the adhesive prior to deformation of the facing assembly. Finally, the facing is cut or shaped to the desired size and stored for later use.

As will be appreciated, the release paper layer may be easily stripped from the pressure-sensitive adhesive immediately prior to attaching the facing to the abrading tool. When the facing or cover is attached only the adhesive on the depressed areas contacts the working face of the tool thereby providing air spaces 30 which impart to the assembly its slight cushioned effect. This effect facilitates the uniform dispersion of the abrasive slurry thereby assuring a more accurate and precise grinding of the arcuate lens surface. It is a further advantage of the present invention that upon the continued exertion of pressure by the tool against the lens face an increasing area of the adhesive comes in contact with the grinding tool to assure that slippage will not occur. Thus, the undulations in the facing provide not only a means whereby uniform dispersion of the abrasive is elfectuated but also provide a means for eifectuating a more secure bonding between the tool member and the facing when greater pressure is applied. Additionally, since the foil is a solid continuous material, the slurry does not have an opportunity to rupture the adhesive bond between the facing and the tool and further is less likely to become frayed or form splinters or whiskers which might scratch the lens blank or clog the abrasive slurry pumping apparatus.

. As will be apparent to persons skilled in the art, various modifications and adaptations of the structure above-described will become readily apparent without departure from the spirit and scope of the invention, the scope of which is defined in the appended claims.

I claim:

1. A cushioned protective facing assembly for a lens abrading tool comprising an imperforate layer of foillike material having the same general shape as the working face of the tool; and a continuous coextensive adhesive layer in intimate contact with one surface of said foil-like layer, both of said layers having a plurality of slots spaced about the periphery thereof and extending inwardly toward the center of the facing over at least half the distance to said center, said layers being undulatory throughout so as to provide a plurality of air pockets between the working face of the tool and the protective facing.

2. A cushioned protective facing assembly as set forth in claim 1 wherein said imperforate layer is sheet metal of foil thickness having a generally arcuate outer edge.

3. A cushioned protective facing assembly for a lens abrading tool comprising an imperforate layer of foillike material; a continuous coextensive adhesive layer in intimate contact with one surface of said foil-like layer, both of said layers having a plurality of slots spaced about the periphery thereof and extending inwardly toward the center of the facing over at least half the distance to said center, said layers being undulatory so as to provide a plurality of air pockets between the Working face of the tool and the protective facing; and a release layer contacting and covering said adhesive layer prior to attachment of the facing to the tool.

4. A cushioned protective facing assembly as set forth in claim 3 wherein said imperforate layer is sheet metal of foil thickness and said adhesive is a rubber based pressure-sensitive material.

5. A cushioned protective facing assembly for a lens abrading tool comprising an imperforate layer of metal foil having a generally arcuate outer edge and a thickness of about 0.001 to 0.005 inch; a continuous imperforate tacky layer of pressure-sensitive, rubber based adhesive in intimate contact with said metal foil, both of said layers having in registry at least four radially extending slots spaced about the periphery thereof and extending inwardly about two-thirds of the radial dimension, said layers further being undulatory throughout to provide a plurality of cushion air pockets between the tool and the facing; and a layer of release paper contacting and completely covering said adhesive layer prior to attachment of the facing to the tool.

References Cited UNITED STATES PATENTS 2,372,535 3/1945 Walker 51-284 X 2,752,738 7/1956 Seifert 51-2-84 X 3,144,737 8/1964 Faas 51-284 X 3,151,347 10/1964 Tindall 5l284 X 3,225,497 12/1965 Brandt 5l284 X ROBERT C. RIORDON, Primlary Examiner.

D. G. KELLY, Assistant Examiner. 

1. A CUSHIONED PROTECTIVE FACING ASSEMBLY FOR A LENS ABRADING TOOL COMPRISING AN IMPERFORATE LAYER OF FOILLIKE MATERIAL HAVING THE SAME GENERAL SHAPE AS THE WORKING FACE OF THE TOOL; AND A CONTINUOUS COEXTENSIVE ADHESIVE LAYER IN INTIMATE CONTACT WITH ONE SURFACE OF SAID FOIL-LIKE LAYER, BOTH OF SAID LAYERS HAVING A PLURALITY OF SLOTS SPACED ABOUT THE PERIPHERY THEREOF AND EXTENDING INWARDLY TOWARD THE CENTER OF THE FACING OVER AT LEAST HALF THE DISTANCE TO SAID CENTER, SAID LAYERS BEING UNDULATORY THROUGHOUT SO AS TO PROVIDE A PLURALITY OF AIR POCKETS BETWEEN THE WORKING FACE OF THE TOOL AND THE PROTECTIVE FACING. 